Until the present invention, several insulation fault testing methods have been used. In the conventional water test system, rolls of multiplex cable are put in a water tank and voltage is applied. The results can show the existence of a fault or faults in a roll of cable but the fault locations are not known. This system is very time consuming. In another test system, cable is wound from one spool to another with a water test in between. This test is dangerous to operating personnel. In both of these systems, water flows into the cable through faults which contaminates the conductor and which makes patching of such faults difficult and ineffective.
When all strands of multiplex cable are insulated, faults can be located by sending the multiplex cable through a spark tester. However, since most multiplex cable contains one bare conductor, a system which would test each insulated strand while isolated from the bare strand was needed. U.S. Pat. No. 3,988,666 accomplished this by unplexing multiplex cable, isolating the bare strand, spark testing the insulated strands and replexing the multiplex cable.
These prior art methods are costly because they involve additional handling, consume time and often one test will apply to only one type of multiplex cable, i.e., one bare strand or all insulated strands.